1. Field of the Invention
The present invention relates to a drive apparatus of a liquid crystal display device and, more specifically, to a drive apparatus of a passive and active matrix liquid crystal display device.
2. Description of the Related Art
A liquid crystal display device of conventional type carries therein X and Y electrodes in a matrix, and performs display by driving a liquid crystal material disposed at electrode intersections.
FIG. 1 is a schematic diagram showing the configuration of such a conventional liquid crystal display device. The liquid crystal display device is configured by a liquid crystal module controller 101, a liquid crystal module (LCM) 102, a power supply 111, and a regulator 103.
The liquid crystal module (LCM) 102 includes a liquid crystal panel, a common/segment driver which drives the liquid crystal panel, and a module controller (not shown) which controls the operation of the driver or others, for example.
The liquid crystal module controller 101 includes a data transfer clock generation circuit 105, a display data generation circuit 106, a synchronizing signal generation circuit 107, and an alternating signal generation circuit 108. To the liquid crystal module (LCM) 102, these components provide supplies of, respectively, a transfer clock CLK, display data DATA, horizontal and vertical synchronizing signals (HSYNC, VSYNC), and an alternating signal (hereinafter, also referred to as alternating signal DF). The liquid crystal control module device 101 is connected to a microprocessor unit (MPU) 110 via a system bus 117, and performs display control for the liquid crystal module (LCM) 102 under the control of the MPU 110.
The liquid crystal module (LCM) 102 receives a drive current from the power supply 111 through the regulator 103.
As described above, the liquid crystal module (LCM) 102 receives an alternating signal, and the liquid crystal panel is subjected to alternating drive. That is, the drive voltage for application to the common electrode and the segment electrode of the liquid crystal module (LCM) 102 is reversed in polarity in accordance with an alternating signal.
FIG. 2 schematically shows an alternating signal and a drive current for supply from the regulator 103 to the liquid crystal module (LCM) 102. As shown in FIG. 2, every time the alternating signal is reversed, a high level of current I2 flows with a spike or surge peak. The current flow of such a high level has been resulted in problems of causing unstable or erroneous operation of the liquid crystal display device. As an example, refer to Japanese Laid Open Patent Application Kokai No. H07-253565.
When the regulator 103 has the current supply capability of about a level of a normal current (I1 of FIG. 2), there needs to include a large-capacity capacitor for supply of the peak current I2. In this instance, however, the device size is increased, and the cost is also increased.
Considered here is a case where the regulator 103 is increased in its current supply capability to a level possible to supply the peak current I2. In this case, however, the regulator 103 will be mostly involved in the supply of the normal level of current I1 when it is in operation. The regulator 103 thus operates mainly in the region with poor conversion efficiency, and thus the power consumption is increased.